1. Field of the Invention
The present invention relates to a paper sheet discriminating apparatus and method for deciding a kind and genuineness of a paper sheet such as a bill and, more particularly, to a paper sheet discriminating apparatus and method for discriminating a paper sheet such as a US dollar bill which may have a pattern (image) dislocated with respect to the contour.
2. Description of the Prior Art
FIG. 1 is a schematic diagram showing a relation of an example of the shape of a bill and an area to be discriminated. Generally, a bill 1 such as a Japanese bill has a fixed external shape or contour 1a, and this contour 1a and a pattern 1b have fixed locations. By using these fixed relations, the bill discriminating apparatus discriminates the bill 1 by blocking the image data in a discrimination area 2, as sampled from the external shape of the bill 1, to match the patterns.
When the paper sheet such as the bill being transferred is to be discriminated on its kind, genuineness, damage, breakage and so on by the paper sheet discriminating apparatus, the discrimination has to consider the xe2x80x9chiatusxe2x80x9d due to the breakage or fold of the paper sheet or due to the xe2x80x9cdisplacementxe2x80x9d or the xe2x80x9coblique dislocationxe2x80x9d to occur during the transfer.
A discrimination apparatus considering the chip due to the breakage or fold of the paper sheet is disclosed in Japanese Patent Application Laid-open No. 8-263718, for example. In this disclosed apparatus, the chipped portion, if any in the contour, of the paper sheet is complemented to a complete contour on the basis of a plurality of peripheral pixel data so that the pattern recognition is performed by blocking the complete contour. According to the above disclosure, the image data to be used for discriminating the paper sheet can restore those near the data before chipped, thus providing an effect that the misjudgment percentage can be lowered.
On the other hand, a discrimination apparatus considering the displacement and the oblique dislocation to occur in the paper sheet being transferred is disclosed in Japanese Patent Application Laid-open No. 6-318245, for example. In this disclosed apparatus, a line sensor is used to fetch the image data of the whole area of the paper sheet running at a high speed to write the detection time array (in which the time period for detecting the boundaries of the paper sheet and the background and the element numbers corresponding to the read pixel locations are made to correspond) in a buffer memory. Then, the gradient of the read image is corrected by oblique correction means, and the four corners of the bill are specified to determine the center location coordinates from the coordinates of the four corners so that the effective area in the buffer memory is decided with reference to the determined coordinates. The monochrome image of the effective area is equally divided, and the characteristic data of the equally divided density image are determined so that a binary threshold value may be decided by extracting a constant statistical quantity from the characteristic data. In the apparatus, the paper sheet is partially read to recognize its kind and genuineness, thus providing an effect that the recognition is not adversely affected even when the paper sheet is dislocated by the transfer.
In the discrimination apparatus for discriminating the kind and genuineness of the bill, as described above, consideration has been taken in the prior art into the displacement or the oblique dislocation but not into the case in which the image of the pattern is dislocated with respect to the contour frame. The bill such as the US dollar bill is circulated even if the external contour 1a and the pattern 1b of the bill 1 are dispersed, as shown in FIG. 2, due to the cutting dislocation. In the paper sheet discriminating apparatus for deciding the kind and direction of the bill by recognizing the image characteristics of the bill, the image in the discrimination area 2 to be discriminated is blocked on the basis of the external shape determined, and the bill is discriminated with the blocked image information. As shown in FIG. 2, however, the image in the blocked discrimination area 2 is dislocated from the pattern 1b so that the discrimination such as the pattern matching cannot be precisely performed. In other words, there arise a problem that the rejection of bills frequently occurs. In the circulated bills, on the other hand, it seems that the cutting dislocations are mostly the parallel ones and extremely few oblique ones, but no consideration is taken into the parallel dislocations. When the target of discrimination is a bill such as the US dollar bill the pattern of which may be dislocated with respect to the sides of the external shape, the discrimination apparatus of the prior art may be unable to recognize the normal bill, thus raising a problem that the discrimination percentage is lowered.
The present invention has been conceived in view of the background thus far described and has an object to provide a paper sheet discriminating apparatus and method capable of discriminating even a paper sheet such as a US dollar bill, in which the location of a pattern is dislocated from the periphery due to a printing shear or a cutting dislocation, efficiently without any drop of the discrimination percentage by using the image of the paper sheet.
The present invention relates to a paper sheet discriminating apparatus and method for deciding the kind or genuineness of the paper sheet such as the bill. According to the present invention, the above-specified object is achieved by a paper sheet discriminating apparatus for deciding at least the kind of a paper sheet on the basis of its pattern by sampling the image of its whole surface, wherein the improvement resides in that the dislocation of the pattern, as viewed from the contour, is detected on the basis of the marginal length of said paper sheet from the outer periphery to the pattern, thereby to correct a pixel position for providing a base point for the image recognition of said paper sheet, with the detected dislocation.
The object of the present invention is also achieved by a paper sheet discriminating apparatus for discriminating a paper sheet in terms of its pattern by irradiating said paper sheet with a light to receive at least the reflected one of a transmitted light and a reflected light obtained from said paper sheet, comprising: contour center coordinate extracting means for determining the center coordinates from the contour of said paper sheet on the basis of image data of said paper sheet; and marginal length extracting means for extracting the marginal length of the outer periphery of said paper sheet from the contour to the center coordinates, wherein the difference in the marginal lengths from the contour edges of the individual two sides of said paper sheet in the longitudinal and transverse directions is determined by said marginal length extracting means so that the center coordinates of said pattern may be obtained by correcting the center coordinates from the contour, as determined by said contour center coordinate extracting means, by using said difference. Moreover, the object is achieved more effectively by a paper sheet discriminating apparatus, wherein the difference of said marginal lengths is determined at the portion, where the channels at the identical position in the transfer direction and the lines in the transfer transverse direction are identical, to prevent an excessive correction by substituting a predetermined maximum when said difference is no less than a predetermined value, and to determine an average value by excluding the maximum and the minimum of the marginal lengths of a plurality of portions of each side.
On the other hand, the object of the present invention is achieved by a paper sheet discriminating method for discriminating a paper sheet in terms of its pattern by irradiating said paper sheet with a light to receive at least the reflected one of a transmitted light and a reflected light obtained from said paper sheet, comprising: determining the difference between the marginal lengths from the individual two side edges of said paper sheet in the longitudinal and transverse directions, to determine the center coordinates of said pattern by correcting the center coordinates determined from the edges of the individual two sides of said paper sheet with said difference; and determining the difference between said marginal lengths at the portion, where the channels at the identical position in the transfer direction and the lines in the transfer transverse direction are identical, to prevent the excessive correction by substituting a predetermined maximum when said difference is no less than a predetermined value, and to determine an average value by excluding the maximum and the minimum of the marginal lengths of a plurality of portions of each side.